bball7754 Posted July 8, 2011 Share Posted July 8, 2011 I’ve had a distributor issue with my Crossflow for… well, too long. I won’t bore everyone with the full saga, but I’m at a point where I’m ready to replace my Aldon Ignitor with a Pertronix Ignitor II. According to Pertronix tech support, the curve on the distributor is 5 degrees at 1000 rpm to 25 degrees at 4000 rpm. My Crossflow needs 12-14 at idle, which is more like 1200 rpm. Ignoring whether the actual curve suits the cam/carbs, etc., I thought I’d be ok. I thought that moving the idle advance up by, say, 7-9 degrees to 12-14, would result in the total advance being increased by 7-9. So max would be 7-9 plus 25, or 32-34, which is about right (I think 34 is preferred). Pertronix tech support said, no, if I set the idle to 14 the total advance would be 14 plus the 25 per the original curve spec for a total of 39. Which is too much. Is he right? Thanks. Steve Link to comment Share on other sites More sharing options...
twobone Posted July 8, 2011 Share Posted July 8, 2011 I agree his answer sounds very strange. I know its not answering your question, my distributor is stamped with a spec of an advance of 25 at 4,000 RPM. I had 12+ degrees of advance at idle which led to a very high advance at high revs. I recently dialed it back to about 8 at idle. The car now runs more smoothly, although with less mid range. I think there is a big difference in settings depending on what type of head you have (unleaded vs. leaded) Link to comment Share on other sites More sharing options...
Ian7 Posted July 10, 2011 Share Posted July 10, 2011 He's partially right. That dizzy is designed to open up an additional 25 degrees over the rpm range of 1000 thru 4000. Initially you might think that it merely adds 25 to whatever you set at idle, and you'd be right if you set your idle at 1000 rpm, but if you set your idle advance at 1200 rpm rather than the 1000 the dizzy assumes, the dizzy will have already started to open up during that (admittedly small) 200 rpm difference. Maybe that's only a couple of degrees though.... So, if you set 12 degrees at 1200, the dizzy is going to add whatever it has left to offer between 1200 and 4000, say 23 degrees or so, so in the end your advance at 4000 would be 12+23 = 35; just about right in my opinion. Link to comment Share on other sites More sharing options...
Dave W Posted July 12, 2011 Share Posted July 12, 2011 To be on the safe side, I would mark the engine damper at the 34 or 35* that you want and checking the total advance at 4000 RPM with a timing light. I would also run the engine a little higher to verify that all the advance is in at the 4000 RPM. Dave W Link to comment Share on other sites More sharing options...
bball7754 Posted July 12, 2011 Author Share Posted July 12, 2011 (edited) Ian - Doesn't it really open up an additional 20 degrees between 1000 and 4000? It's at 5 degrees at 1000, and 25 at 4000, which seems like an additional 20 degrees. I had asked for the static advance, but all they gave me was a chart with the advance starting at 5 degrees at 1000 rpm. Is it really possible that the static advance is less than 5 degrees, and that the advance has actually opened up X degrees by 1000 rpm? Steve Edited July 13, 2011 by bball7754 Link to comment Share on other sites More sharing options...
cmaxcliff Posted July 13, 2011 Share Posted July 13, 2011 The ignition unit won't change your advance curve. It is important that you set the timing with a light at full advance for the best wide open throttle performance. If the driving manners are poor then you must have the distributor re-curved to fit your engine combination. 25* total distributor advance seems about right. Set the timing at full advance and see how it drives. I don't see how changing to a Pertronix will change how the car drives unless it has a miss. Link to comment Share on other sites More sharing options...
bball7754 Posted July 13, 2011 Author Share Posted July 13, 2011 The Pertronix was/is my backup. I sent my Aldon to England to have the curve changed, as what I had was known to be poor. The modified Aldon now causes my tach to bounce all over the place. I've replaced the battery, ignition and HT leads (both were due anyway), changed the low voltage connectors, and confirmed the alternator output. None of them fixed the tach issue. Have another Aldon on loan from a UK Caterham owner who has a spare. With that distributor installed, I have no tach problems. The Pertronix was purchased as an alternate when I thought that my distributor was lost in transit to the UK. See, I told you it was a saga. So, I have a distributor with, theoretically, the correct advance curve for my engine and specs. But don't have a working tach with it installed. And have a Pertronix that let's the tach work, but not sure about the advance curve. Am I having fun, or what? Link to comment Share on other sites More sharing options...
Ian7 Posted July 17, 2011 Share Posted July 17, 2011 Ian - Doesn't it really open up an additional 20 degrees between 1000 and 4000? It's at 5 degrees at 1000, and 25 at 4000, which seems like an additional 20 degrees. I had asked for the static advance, but all they gave me was a chart with the advance starting at 5 degrees at 1000 rpm. Is it really possible that the static advance is less than 5 degrees, and that the advance has actually opened up X degrees by 1000 rpm? Steve Unless there's something really odd with the unit you have, it is a simple centrifugal device that opens 25 degrees between 1000 rpm and 4000 rpm, so it adds 25 to whatever you start at. The 5 degrees is their arbitrary starting suggestion (which most of us think is too little). My point was that if you set idle timing at an rpm above 1000, you've already used up a little of the 25 it would have added had you set idle at 1000. At risk of telling you what you already know, in these simplistic mechanical dizzies there are little spring loaded counterweights that get flung out radially by the spinning action; nothing happens below 1000 because the spring is stronger than the cf force; once you reach 4000 (in this case), the weights reach a hard stop and dont move any further, and advance stays at "idle setting + 25 degrees" no matter how much higher you rev it. Link to comment Share on other sites More sharing options...
twobone Posted August 2, 2011 Share Posted August 2, 2011 How did the pertronix distributor run? Was it the english ford unit? They sell one specifically for english fords for $215 that includes and ignitor built in. I'm considering this as a plug and play replacement for my rather suspect old Lucas electronic unit Link to comment Share on other sites More sharing options...
bball7754 Posted August 3, 2011 Author Share Posted August 3, 2011 Yep, part noD190509 (side exit, no vacuum advance). Unfortunately, it's still sitting on the workbench. I had a brain cramp when I put it in and didn't connect the low voltage leads. Tried to start it and flooded it. Connected them, and then had a heck of a time getting it to start. Put my borrowed one back in, and it's been too hot to work on it since. If you buy it and get the Flamethrower II coil, it (the coil) won't fit in the ignition coil bracket for the Lucas coil. Ask me how I know. Steve Link to comment Share on other sites More sharing options...
Sabbot Posted August 3, 2011 Share Posted August 3, 2011 (edited) This may help, last weekend I checked the timing on my 1700cc supersprint (which runs a petronix distributor) with a strobe. It has had a fairly lumpy idle ever since I got it last year but I always put that down to a modified cam. Anyway, when I checked the static advance(~800rpm idle) it was set to 6o BTDC when I advanced the igntion up to 12-14o BTDC the idle increased to ~1400rpm and when I dialed back the idle screw to ~800rpm it ran more smoothly. My worry was that running with effectively 14o of static advance the total advance at 6000rpm (which it sits on a reasonable amount of time) would be way too high (when I began to set the timing I had no info on the advance curve for the distributor). Given that it will start and idle anywhere between 6o and 14o BTDC (static) I decided to set the static advance a different way. I set the timing while running at 6000rpm to ~34o BTDC which resulted in a static (800rpm) timing of ~10o BTDC which suggests that the petronix is set for 25o of total advance. That's the info now here comes the question. I noticed while playing around with the timing that at any give rpm above 2000rpm there can be up to 10o of bounce in the timing as the strobe illuminated timing mark drifts "bounces" around. I don't know if that is due to a worn distributor or the nature of the multiple spark MSD unit that controls the coil. I would have suspected that there may be some error in the strobe pick up due to multiple spark generated below 3000rpm but my understanding of the MSD 6AL unit is that it reverts to a single spark per bang above 3000rpm. Given that having set the timing and resynchronized the carbs it still feels a little sluggish I'm wondering if the distribtor is worn. This may seem like a dim questions but after owning british sports cars for >30 years I've only just bought a strobe (static stiming by bulb is fine with contact breakers) and therefore I'm not sure how much "timing bounce" to expect. Any thoughts? Edited August 3, 2011 by Sabbot Link to comment Share on other sites More sharing options...
twobone Posted August 4, 2011 Share Posted August 4, 2011 Was your petronix a stock item? I got a copy of the english ford unit advance curve and it says that at 940 rpm is would be at 8 degrees of advance with a max of 24 at 3050. That's only 16 degrees of advance difference. That would lead to a massive idle advance. Link to comment Share on other sites More sharing options...
bball7754 Posted August 4, 2011 Author Share Posted August 4, 2011 Sabbot - I have the same "bounce" with my timing light, but have it at idle on up. Just have a Lucas Sport coil. Would also like to know the cause. Towbone - It's a stock distributor. Actually bought it from Summit Racing - they had a good price. I emailed Petronix support asking about the advance curve, and they answered with this, which seems like different info than what you've received: Link to comment Share on other sites More sharing options...
twobone Posted August 4, 2011 Share Posted August 4, 2011 Ouch - I ended up biting the bullet to order an Aldon Distributor with ignitor ($400 with shipping and exchange) This was the spec for the one I ordered: As an approximation the idle figure is 10 deg B.T.D.C and full advance approx 34 deg BTDC @ 5400 rpm. These are engine rpm. If you have any queries with this please contact our Sales Department on 01384 572553. Regards Sales & Marketing Department Aldon Automotive Ltd Breener Industrial Estate Station Drive Brierely Hill West Midlands DY5 3JZ Link to comment Share on other sites More sharing options...
bball7754 Posted August 5, 2011 Author Share Posted August 5, 2011 If it makes you feel any better, I spent about $200 having Aldon change the curve on my distributor, then when I thought it was lost in the mail spent another $215 or so on the Pertronix. So I've invested about $400 in distributors - and the one I'm using is borrowed!! Ah, the joys of the Crossflow. Link to comment Share on other sites More sharing options...
Sabbot Posted August 5, 2011 Share Posted August 5, 2011 I'm not sure if the petronix unit on my supersprint is stock or not, but I suspect not given that on careful inspection it has a bunch of roughly engraved numbers on the side which I think (can't confirm) were probably added when the engine rebuild work was done by the previous owner. I think at some point I'll have to get this on a dyno and figure out best settings etc. It really doesn't start to work well untill it gets beyond 3000rpm, that said it's a blast from 3000-6000. Link to comment Share on other sites More sharing options...
twobone Posted August 23, 2011 Share Posted August 23, 2011 Finally go the proper curved Aldon unit installed. Initial impressions are: -No more lazy spark -Nice fat mid range around 3,000 I'm going for a twisty road blat tonight so I will let you know about the top end tomorrow Link to comment Share on other sites More sharing options...
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